More evidence as if any were required, that POPLA assessors can be as moronic as they like and get away with it.
Never mind, the POPLA decision is not binding on you. You do not have to pay anything. If you continue to follow the advice, you will not pay a penny.
You can ignore the letter from UKPC. You will also receive some debt recovery letters threatening all sorts of stuff. Again, you can safely in=gnore all of this. Debt collectors are powerless to actually do anything except to try and make the low-hanging fruit on the gullible tree pay up out of ignorance and fear.
When you receive a Letter of Claim (LoC) come back and we will provide a response. You will, in due course, receive an N1SDT Clim Form from the CNBC. Again, we will provide a suitable defence. Eventually, I can tell you with greater than 99% certainty that the claim will either be struck out or discontinued and that will be the end of the matter.
As I say, you can safely ignore everything else you receiver except the LoC and the claim. Come back when you do receive those.